Although NF-L may not be a disease-specific peripheral biomarker, its presence in the blood and CSF has aided in the early detection, diagnosis, prognosis, and prediction of time-to-symptom onset in all-cause dementia, including frontotemporal dementia (FTD), amyotrophic lateral sclerosis (ALS), Huntington's disease, Parkinson's disease (PD), human prion disease (PrD) and AD (20–25). Here, NEFL is linked to Parkinson disease.